1. Field of the Invention
This invention relates to the signal transmission and reception art and more particularly to an arrangement for providing a visually and/or audibly detectable signal in a vehicle indicating the presence and/or the proximity and/or relative direction of an emergency vehicle thereto.
2. Description of the Prior Art
Many vehicles, and in particular passenger vehicles, incorporate, as part of their design features, the minimization of external noises penetrating into the passenger compartment. Further, many advertisements for such passenger vehicles particularly point out and stress the quiet conditions in the passenger compartment through the exclusion of externally generated noise, even including the sound of the engine, in the vehicles. While such quietness in the passenger compartment provides a more pleasant atmosphere during riding therein, it has presented a major problem with regards to the driver of such a vehicle being informed of the presence of emergency vehicles such as ambulances, fire equipment, police vehicles or the like.
Such emergency vehicles generally incorporate not only a visual signal, such as a steady or flashing red light, but also various types of audible signal generating devices such as sirens, growlers or the like. The flashing lights require that the emergency vehicle be within direct line-of-sight of the vehicle to be warned of its presence and also that the driver thereof in some way see such a light.
The improved audio insulation qualities of the passenger vehicles has resulted in an increase in the decible level of the noise producing devices of the emergency vehicles. Thus, many present emergency vehicles incorporate such audible signal devices having an intensity level approaching that of physical harm to listener. That is, pedestrians and other people, not in vehicles, can be subjected to auditory damage due to the intensity of such sound. Therefore, the level of intensity available for such audio signal devices in emergency vehicles has approximately approached the limit. However, even sounds generated at this high audio intensity in many instances still do not provide a sufficient warning time to the driver of well audio-insulated vehicles.
In addition, it is often desired not only to know of the presence of an emergency vehicle in the vicinity of the passenger vehicle but also, for greater safety, it is desirable that the driver of the passenger vehicle also be provided with information indicating the relative separation between the vehicle and the emergency vehicle and also, in many instances, the relative direction thereto.
Many systems have heretofor been designed to provide indication of relative distance, that is range, and direction of one vehicle from another. Highly sophisticated systems, such as those utilized in fire control radar, missile guidance and the like provide excellent information content concerning the range and/or relative direction, but are much too expensive and complicated for utilization in a passenger vehicle to indicate the presence of an emergency vehicle and positional relationship to the passenger vehicle.
In other prior art systems that have attempted to provide the driver of, for example, passenger vehicles, with knowledge of the presence of an emergency vehicle in proximity thereto, there has been incorporated merely a radio signal generated in the emergency vehicle and this signal is broadcast by the emergency vehicle for reception in the passenger vehicle. U.S. Pat. No. 3,233,217 provides such a system in which a different tone is utilized for different emergency vehicles and thus the presence as well as the type of emergency vehicle can be detected by the driver of the passenger vehicle or other non-emergency vehicles. Thus, while providing an indication of the presence of such an emergency vehicle there is no indication as to the relative separation, or proximity, between the receiving vehicle and the emergency vehicle nor was there any indication provided to the driver as to the relative direction of the emergency vehicle from the driven vehicle.
U.S. Pat. No. 3,010,499 provides a system capable of installation in all vehicles and the system is responsive to the audio signal output of the emergency vehicle. A microphone and appropriate circuitry are utilized for converting the sound received by the microphone in the other vehicles into a visual or audible signal in the vehicle. However, no indication of the relative separation or relative direction is provided.
Thus, there has not heretofore been provided an inexpensive, reliable system for providing the driver of vehicles with an indication not only of the presence of an emergency vehicle but also of the relative separation and relative direction of the emergency vehicle from the driven vehicle.